It is known to use magneto-optical discs as a recording medium of large capacity on which data is rewritable.
In a magneto-optical disc apparatus for recording data on the magneto-optical disc or reproducing data therefrom, a clock signal for reading data recorded on the disc is formed by sampling a high frequency signal derived from a photo-detector used to detect, for example, a servo pit formed on the magneto-optical disc by a sampling pulse.
In the above-mentioned magneto-optical disc apparatus, a timing (phase) at which the high frequency signal from the photo-detector is sampled is displaced due to movement of the elements, their temperature characteristic or the like. For example, a signal is recorded on the magneto-optical disc by a laser light. In this case, a signal recorded portion formed by the laser light is positionally displaced depending on the output state of the laser light. FIGS. 8A and 8B are diagrams illustrating different positions at which the signal recorded portions may be formed. In one case, a laser light of relatively low intensity is generated for a long time period in response to a pulse signal L.sub.1 shown in FIG. 8A. In the other case, a laser light of relatively high intensity is generated for a short time period in response to a pulse signal L.sub.2 shown in FIG. 8B. Although the laser laser outputs are substantially the same, recorded portions P.sub.1 and P.sub.2 formed by the respective laser lights are formed from the centers of the irradiated portions so that they are displaced from each other by .delta..
The displacement between the sampling timings directly leads to the displacement between a data read clock signal and recorded data. There is then a risk that an error will frequently occur in reading, for example, the recorded data. To solve this problem, in the prior art there is no other solution than adjusting at every circuit by using a delay line or the like. Thus, the adjusting operation requires much labor and time.